1. Field of the Invention
The invention relates to a data transmission system and, more particularly, to a bidirectional data transmission system.
2. Description of the Related Art
FIG. 1 schematically shows data transmission of a transmission system 10, wherein a video graphics array (VGA) interface or a digital visual interface (DVI) is used to transmit data between a display and a host system. Generally, a VGA interface or a digital visual interface (DVI) is integrated with display data channel (DDC) to become a signal transmission line. The transmission system 10 receives input signals from keyboard 13, mouse 14, remoter 15, or other input devices via the input/output interface (I/O interface) 121 of a display 12, and processes the input signals, and outputs an output signal to a host system 11 via Universal Serial Bus (USB) lines. Then, the host system 11 executes tasks assigned by the output signal, and transmits image data to the display 12 via VGA interface or DVI transmission line connected with a VGA graphic card (not shown) of the host system 11.
In order to transmit the output signals of the input devices 13, 14, and 15 to the host system 11, an extra USB line should be used for the display 12. However, it will increase not only the cost of the display 12, but also the disorder degree of the line arrangement of the peripherals of the host system 11.